Some gas turbine fuel controls are regulated by an electronic controller (EEC). The EEC sends control signals to a metering valve within the fuel control. The metering valve, in turn, regulates the weight flow of fuel to the gas turbine engine.
An interface is required between the metering valve and the EEC. The interface provides feedback signals which apprise the EEC of the position of the metering valve. Fuel flow to the gas turbine engine may be accurately controlled thereby.
Typically, the interface is provided by a linkage system between the metering valve and the EEC. The linkage system includes a linkage attaching to and positioned by the metering valve, a position sensor, such as a resolver, which sends feedback signals to the EEC and a segment gear assembly arranged between the linkage and the position sensor. The resolver has a central rotor which has a gear attached thereto. The gear, and the rotor attached thereto, are positioned by the segment gear assembly.
The resolver is a variable transformer. Rotation of the rotor via the linkage varies the output of the transformer to provide feedback signals to the EEC as to the position of the metering valve.
Fuel controls for gas turbine engines may be subjected to vibratory fields. Some vibratory fields may stimulate resonant modes within the position sensor resulting in excessive wear in the connection (i.e the gear attaching to the rotor and the segment gear assembly) between the position sensor and the linkage. The wear may increase the backlash in the linkage system. The EEC may not be provided with accurate feedback as to the exact position of the fuel metering valve. Significant fuel flow errors resulting in engine overspeed or shutdown may then occur.